WASHINGTON (Reuters) – Dark matter, mysterious invisible objects that make up most of the mass of galaxies including our own Milky Way, again confuses scientists with new observations of distant galaxies that contradict the current understanding of its nature.
Research published this week revealed an unexpected discrepancy between observations of dark matter concentrations in three massive clusters of galaxies comprising trillions of stars, and theoretical computer simulations of how dark matter should be distributed.
“Either an ingredient is missing in the simulations, or we have made a fundamentally wrong assumption about the nature of dark matter,”
Dark matter is the invisible glue that holds stars together inside a galaxy. It also creates an invisible scaffold that allows galaxies to form clusters. But it has very peculiar properties. It does not emit, absorb or reflect light and does not interact with any known particles.
The bulk of the matter in the universe, approx. 96%, is thought to be dark matter with ordinary matter – the visible things that make up stars, planets and humans – only 4%.
The presence of dark matter is known only through its gravity on visible matter in space. It differs from the similarly enigmatic and invisible dark energy that is considered a space property and drives the accelerated expansion of the universe. Dark energy is repulsive. Dark matter attracts through gravity.
The new study involved observations from the Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope in Chile.
When light from distant sources such as distant galaxies moves through matter like another galaxy or cluster of them, the light is deflected and bent – a phenomenon called “gravity lens”, said astrophysicist and study author Massimo Meneghetti from the Observatory of Astrophysics and Space Science in Bologna and National Institute for Astrophysics in Italy.
The new observations showed that gravitational lensing effects produced by galaxies located inside the huge galaxy clusters were far stronger than current dark matter theory predicted, suggesting an unexpectedly high concentration of dark matter in these galaxies.
“This is quite surprising,” Meneghetti said.
Reporting by Will Dunham; Editing by Sandra Maler